What is the Difference Between a Heat Pump and a Geothermal Heat Pump?

If you are considering using a heat pump for your home heating and air conditioning, you may want to know the difference between a heat pump and a geothermal heat pump.  They both have the same function — pumping heat from one location to another.  In summer, they pump heat from inside your home to the outside where it can be dispersed.  In cold weather, they gather heat from outside and pump it into your home.  The major difference in the two is their outside energy source.  A standard heat pump draws heat out of the cold outdoor air; a geothermal heat pump draws heat out of the earth which remains at a stable temperature throughout the year.  For this reason, a geothermal heat pump is often called an earth source heat pump and a standard heat pump may be called an air source heat pump.

How Heat Pumps Work

Air source heat pumps and geothermal heat pumps both use refrigerant to collect heat from outside your home and deliver it into your home in the winter.   Refrigerant has the ability to rapidly expand and absorb heat and then rapidly condense and shed the heat in the process.  Inside your home, the heat may be discharged through a coil in an air handler or furnace, or it may be released in a radiant heat system.  In the summer, the refrigerant flow is reversed and it collects heat inside your home and takes it outside, effectively cooling your home by removing heat.

 

Earth Loop or Outdoor Coil

How the system collects heat outside is the basic difference between a heat pump and a geothermal heat pump.  In a air source heat pump, a condensing unit sits outside the house.  It contains a coil that is composed of copper tubing and fins like you might see on the back of a window air conditioner or a car radiator.  When heating your home the refrigerant cycles through the copper tubing and collects heat from the outdoor air.  When cooling your home, it collects heat inside and sheds it in the outdoor coil where it radiates out through the coil fins.

With a geothermal heat pump, an earth loop is buried in the ground.  The earth loop is a closed loop made of high-density polyethylene pipe, chosen because it won’t corrode or rot and has a life expectancy of 200+ years.  Earth loops come in various designs depending on the size of the lot, the type of soil and other factors.  Liquid flows through the earth loop and the temperature of the water becomes the same as the temperature of the soil around it.  The water cycles through a heat exchanger where the refrigerant captures heat in the winter. The water is cooled because heat is drawn from it.  It circulates through the earth loop and warms back up, ready to offer heat to the refrigerant. Through the use of a reversing valve, the refrigerant releases heat into the water in the summer.  The heated water circulates through the loop and is cooled.

 

Pros and Cons of Geothermal Heat Pumps

The primary disadvantage of a geothermal heat pumps is that it is more expensive in terms of the equipment.  They need to be viewed as a long-term investment that will save you money over many years.  If you aren’t committed to your home for 7-10 years minimum, a geothermal heat pump might not be cost-effective.

The advantages include their very high efficiency.  They are more efficient than air source heat pumps.  In the winter, heat is being collected from the ground, which is warmer than the outside air in most cases.  In the winter, the geothermal heat pump is shedding heat into a source that is cooler than the outside air in most cases.  Therefore, a geothermal heat pump does not have to work as hard to collect and dump heat as an air source heat pump does.  Ground source heat pumps are also quieter because they don’t use a noisy condenser that sits close to the house, and they are the most environmentally sound way to heat and cool your home.

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